Conventionally, in a tire vulcanizer which vulcanizes and molds a green tire, an outer mold (mold), in which the green tire is placed, is heated, and the inner wall surface of the green tire is pressed toward the outer mold while being heated by a high-temperature and high-pressure heating medium being supplied to the inner space of the green tire (to the inside of the bladder). Then, the outer side and the inner side of the green tire are heated by the heated outer mold and the heating medium supplied to the inner space of the green tire, and thereby the green tire is vulcanized.
Note that the conventional tire vulcanizer is configured such that steam as a heating medium is supplied into and circulated through the inner space of the green tire, and such that a heated and pressurized medium, such as nitrogen gas and warm water, is sealed in the inner space.
As a prior art of the tire vulcanizer described above, in which a green tire is heated from the outside thereof, there is an apparatus using a heat medium, as disclosed, for example, in Patent Literatures 1, and 2. In the prior art, a platen (heat plate) is arranged on each of the upper and lower sides of an outer mold in which a green tire is placed, and steam as a heat medium is supplied to the inside of both the platens, so that heat is transferred to the green tire from the outside of the outer mold.
On the other hand, as for a tire vulcanizer in recent years, instead of the above-described heating technique using the heat medium, a heating technique using an electric platen has been proposed from the viewpoint of energy saving, and the like.
As electric heating methods applied to the electric platen, there are known a heating method using a rod-shaped or planar electric heater embedded in the platen (see, for example, Patent Literature 3, described below), and an induction heating method using an electromagnetic coil (see, for example, Patent Literature 4, described below).
Further, the conventional platen described above is formed into a one-piece structure having a doughnut-like disc shape, for facilitating the formation of a heat medium flow path, the attachment to the mold, and the like. However, Patent Literature 5, described below discloses a tire vulcanizing mold in which, in order to obtain a uniform degree of vulcanization over the whole of a tire, the platen is divided in the radial direction thereof, and the rates of temperature increase of heating sections are correspondingly changed.